AN OUTBURST OF A DEEPLY EMBEDDED STAR IN SERPENS

We have discovered a substantial increase in the K-band brightness of a young, deeply embedded star in the Serpens NW star-forming region be tween 1994 August and 1995 July. The photometric history suggests a si milarity to FUor or EXor outbursts. However, the star is more deeply e mbedded than any previous examples of those two types of eruptive even ts. Even in its bright state, the object is invisible in J, only scatt ered radiation is seen in H, the K band is still dominated by scattere d light, and only in L' and longer wavelengths do we see a pointlike s ource. The Serpens Deeply Embedded Outburst Star (DEOS) has been detec ted at 800 mu m, confirming its very young age, Its spectrum between 2 .0 and 2.5 mu m is a very steep, pure continuum, steeper than any publ ished spectrum of a young embedded star. Most likely, the spectrum is thermal radiation from dust enshrouding the young star that completely veils any of the spectral features characterizing less obscured FUors and EXors stars. The outburst luminosity is only approximate to 15 L. , so that the preoutburst luminosity must have been very low. The Serp ens DEOS is probably a young star of very low mass.